Papers by Keyword: Bioabsorbable

Abstract: Polylactic acid (PLA) is a bioabsorbable polymer that is used in a variety of medical conditions. Complex forms of this material are commonly made ​​for fixation and reconstruction of bone fractures. These bioabsorbable implants have been gaining popularity as an alternative to metal implants to stabilize small fractures due to its metal counterpart, avoiding problems such as bone resorption, additional surgery after fixation, infection and possible new fractures. In this paper are shows a number of finite element analysis that aims to determine the functionality of the plates and screws fixation with bioabsorbable material made ​​from PDLLA copolymers 50/50 and 85/15 PLLA-PGA respectively, for fixing and rebuilding of bone fractures in hand.

Abstract: Implants based on titanium alloys, stainless steel and cobalt –chromium have been the primary biomaterials used for load bearing applications and they have been remarkably successful throughout time, but on the long term, there appear a series of inconveniences regarding these metallic implants. Thus, there have been cases of aseptic osteolysis around the implant, with pain and high degree of loosening of the prosthesis which constitutes a limitation of the long term benefits of metallic implants. Therefore, researchers have found new materials for implants, more competitive and efficient. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg is an essential mineral for human metabolism and its deficiency has been linked to various pathological conditions. The main advantages of Mg alloys are its superior mechanical and biocorrosive properties and its biocompatibility. Mg is a very light-weight metal with a lower density than that of biocompatible Ti alloys, which is closer to that of the human bone. In the present paper we shall focus on presenting some biological testing studies of several Mg alloys from the system Mg-Ca, with different percentages of Ca. Three methods have been use for this: determining the ph at different sample incubation times in culture environment; citotoxicity tests made in vitro which: evaluate the contact toxicity by putting the samples in the buckets of cellular culture plates; evaluate the cellular proliferation at the surface of the tested materials by fluorescence microscopy and deflection microscopy; evaluation of toxicity by testing the effect of the extraction liquid resulting from the incubation of the material with testing cell specific culture environment.

Abstract: A novel composite of poly (ethylene glycol) (PEG) functionalized gold nanoparticles (AuNP-PEG) dispersed within Poly (lactic-go-glycolic) (PLGA) films, were prepared to demonstrate the concept of a combined targeted and sustained implant material. This technology offers the promise of improved therapies for difficult to treat tumors such as Gliomas. Gold nanoparticles (AuNPs) synthesized via a modified Turkevich method, were functionalized with thiol terminated polyethylene glycol (PEG), washed using centrifugation, dried, re-suspended in a solution of PLGA in dichloromethane and finally vacuum dried to produce the solvent cast films. The degradation and nanoparticle release profile of these films were studied by immersion in PBS media at 37 °C over periods of up-to 58 days. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was conducted. The release of the AuNPs-PEG nanoparticles during degradation was studied using inductively coupled plasma mass spectroscopy (ICP-MS). It was observed that the AuNP-PEG nanoparticles were individually dispersed within the PLGA and that their addition extended the degradation time of the PLGA film, but did not appear to alter the nature of degradation. The nanoparticle release from the composite films displayed an approximately zero-order release profile.

Abstract: Intramedullary (IM) nails are routinely used to stabilize long bone fractures. They can however lead to stress shielding, pain, migration, obstruct hematopoietic tissue, become a loci for infection, and require subsequent surgical retrieval. Novel intra-osseous scaffold (IOS™) prototypes for fracture healing have been developed to function as a regenerative scaffold to enhance callous formation under mechanically stabilized conditions then resorb. Prototype fixation pins and rod systems were formed from glass-reinforced-glass. Flexion, torsion and shear tests were performed to evaluate the composite pins and rods. A modular rod design was successfully deployed and dilated while in a deformable state. When fitted and gripping the intramedullary canal then set in a rigid state. An obliquely sectioned ovine femur was used as a long bone fracture model for deployment and mechanical verification. Flexural support provided by the intramedullary scaffold was superior to multiple k-wire fixation, while the k-wire approach was more stabilizing under torsional loads. Glass reinforced glass samples were mechanically tested after soaking for up to 4 weeks in saline. Strength and modulus of the composite was reduced to approximately 25% of initial values after 2 weeks.

Abstract: Review of current Anterior Cruciate Ligament (ACL) anchor technologies indicates that many devices facilitate osteointegration but not soft tissue in-growth. The design and preliminary testing of a novel biomimetic in-situ dilating bioabsorbable ACL anchor for simultaneous soft and hard tissue attachment is the subject of this study. The anchor method for this concept has been developed to mimic the mechanical-key configuration observed in a hair root. Reviewed anchor devices are typically interference screw-based. Screw anchors can lead to unnecessary ligament pre-stress, tearing during deployment and poor graft-bone contact. This work demonstrates a new fixation concept specifically developed for use with devices consisting of temperature-sensitive glass-reinforced-glass (GRG) soft tissue conductive biomaterial. Ligament anchorage is accomplished by dilation of the device into the base of a hair-root shaped osteotomy where a ligament with a collar and self tightening knot is inserted beforehand. This method facilitates full ligament-to-bone contact at the osteotomy zone where critical physiological ligament anchorage develops. Ligament pull-out loads equivalent to published results for conventional anchors were achieved using graft analogue. Testing with porcine ligaments resulted in a substantial reduction in ligament pull-out loads. Tibia bone sample constraints combined with the unraveling of the ligament knot were identified as primary factors for low pull-out loads for the porcine ligament tests. Subsequent design iterations will employ a reduction in prototype dimensions in addition to the use of a suture to lock the ligament knot. The hair-root shaped osteotomy and ligament anchor knot elements of this approach may be translated to other fixation systems and methods. By improving macro-mechanical-key interaction between the anchor, bone and ligament, further increase in pull-out forces may be achieved without unnecessary ligament pre-stress and tear damage caused by conventional interference screw threads.

Abstract: To develop a successful bone fixation device that can also release therapeutic agents such as antibiotics one has to consider mechanical, drug release, and biocompatibility properties. We have used bioabsorbable polymers (PLGA 80/20 or PLDLA 70/30) as the matrix and ciprofloxacin (CF) as antibiotic to develop such an implant. Initial shear strengths of the studied ciprofloxacinreleasing screws were 152 MPa (P/L/DL)LA) and 172 MPa (PLGA). Studied screws retained their mechanical properties for least 12 weeks (P(L/DL)LA) and 9 weeks (PLGA) in vitro at the level that ensures their fixation properties. Pull-out tests indicated that the early version of screws have lower values as compared to controls. CF was found to be released after 44 weeks (P/L/DL)LA) and 23 weeks (PLGA) in vitro. It remained in the range of 0.06 – 8.7 µg/ml/day (for P(L/DL)LA) and 0.6 - 11.6 µg/ml/day (for PLGA) after the jump start. Release CF was demonstrated to significantly inhibit S. epidermides growth, attachment and biofilm formation different than controls. Histology showed no difference from plain polymer screws, except for increased giant cells at the implantation site. Accordingly, SR-P(L/DL)LA and SR-PLGA MF implants were considered appropriate to proceed to pilot clinical application.